Harvesting homegrown onions at the correct moment directly impacts the bulb’s flavor, firmness, and capacity for long-term storage. The timing is a biological signal from the plant preparing for dormancy. Pulling bulbs too early results in a smaller, milder onion that will not cure properly. Waiting too long increases the risk of rot or an undesirable second growth spurt. Maximizing the harvest requires observing specific changes in the plant’s structure to ensure stored energy is fully contained within the bulb.
Recognizing the Visual Signs of Maturity
The most noticeable and reliable signal that onions are ready for harvest is the collapse of the plant’s foliage. This process begins when the plant finishes its life cycle and stops transferring energy to the leaves. The heavy, green tops start to yellow and fall over at the neck, where the leaves meet the bulb. This falling over is a physical manifestation of the neck softening as the plant seals itself off for dormancy.
The optimal time to pull the bulbs is when approximately 50% to 80% of the plants have naturally toppled over. Before the tops fall, the bulb is still actively growing and gaining size, so patience is necessary to maximize the yield. The softening of the neck indicates that the transfer of carbohydrates from the leaves into the bulb is complete, initiating the final stage of maturation.
It is important to distinguish this natural collapse from a failure caused by disease or pests. A naturally maturing onion will have a firm bulb and a neck that is pliable but not mushy. Leaving the bulb in the soil too long after the tops fall may cause the plant to re-sprout, which significantly reduces storage life. An over-mature onion is also susceptible to rot, particularly in wet soil conditions.
Preparing the Bulbs for Harvest
Once the first tops begin to fall, initiate a deliberate water deprivation period to gently stress the plant. Completely stopping all irrigation one to two weeks before the expected harvest date is necessary for the bulb to form its protective outer skin. This drying phase thickens the papery outer layer and helps close the neck, protecting the onion from moisture-related storage diseases like sour skin and black mold.
Some gardeners loosen the soil around the bulbs with a garden fork a few days before lifting, especially if the soil is dense. This action severs finer roots, encouraging the plant to halt growth and focus energy on bulb maturation. Manually bending the remaining upright tops, sometimes called “tipping,” is discouraged because it can interrupt the final nutrient transfer. Allowing the plants to collapse naturally ensures the most complete transfer of sugars and the best potential for long-term preservation.
Curing the Onions for Long-Term Storage
Curing is required for any onion intended for extended storage; it is a controlled drying phase that hardens the outer layers and seals the neck. Immediately after carefully lifting the bulbs to avoid bruising, gently brush off large clumps of soil, but avoid washing them with water. Any damaged or bruised bulbs should be separated and used immediately, as they will not cure or store successfully.
The ideal environment for curing is a warm, dry location with excellent air circulation, such as a well-ventilated shed or covered porch, with temperatures between 75°F and 90°F. The bulbs should be spread out in a single layer on screens or racks, or hung in bunches. Ensure they are protected from direct sunlight, which can cause sunscald. The curing period typically lasts two to four weeks, during which the leaves and neck dry completely.
Curing is complete when the neck feels entirely dry and tight, and the outer skins are brittle and papery. This dry neck prevents moisture from entering the bulb, which is the primary defense against rot. After curing, the dried tops and roots can be trimmed to within a half-inch of the bulb. The onions are then ready for storage in a cool, dark, dry place, ideally in mesh bags or crates that allow for continued airflow.